Thyratron with auxiliary electrode



&321166 .June ZO, 1967 A. E. GORDON THYRATRON WITH AUXILIAHY ELECTRODE Filed Aug.

INVENTOR. ALF/?50 GORO/V &KI/

%6 PULSE sou/ece' 4 H .AT TORNEY United States Patett O 3,327,166 THYRATRON WITH AUXILIARY ELECTRODE Alfred E. Gordon, Easton, Pa., assignor to International Telephone and Telegraph Corporation, Ntley, NJ., a corporation of Maryland Filed Aug. 4, 1964, Ser. No. 387,?:40 6 Clains. (Cl. 315-349) This invention relates to gas discharge tubes and particularly to a thyratron having an auxiliary electrode which provides a reduced and relatively constant firing time.

Gas discharge tubes such as hydrogen thyratrons, which provide high voltage pulses, have an inherent time delay between the application of a trigger signal and the initiation of a discharge between the cathode and anode. In addition, due to thermal variations, the firing time changes inversely with the power level at which the tube is operated. One attempted solution for reducing the time lag is the use of two grids, one of which is triggered before the other. The difi'iculties, however, have not been overcome to a suflicient extent for many applications, such as devices utilizing fast high power microwave switching pulses or where a high degree of synchronizaton is required between a plurality of such stages.

It is therefore an object of the present invention to provide more eficient and rapid firing of a gas discharge power tube and to maintain the time relatively constant despite variations in power. These results are achieved by a novel auxiliary electrode which is positioned within but at a higher potential and insulated from the cathode structure. The gas in the different areas of the cathode space is ionized at substantially the same time and the discharge occurs more rapidly and at lower power levels. In addition, the time at which the discharge takes place remains relatively constant under different operating power conditions. The details of the invention will be more fully understood and other objects and advantages will become apparent in the following description and accompanying drawing wherein the figure shows a cross-section of the novel tube structure.

As shown in the drawing, a ceramic envelope 10 encloses a metallic cup-shaped anode structure 12 having an output terminal 14 and an underlying grid control electrode 16. The grid is in the form of a metal disc with an opening providing a circuitous discharge path 18, shown by a dashed line, to the anode for the ionized gas while protecting the anode from the deposit of ernissive material from the oXide coated cathode element 20 and also preventing undesired gas discharge paths. A center shield portion 22 of the grid is supported by webs 24.

The cathode structure is formed of a series of metallic cup-shaped supports 26 mounted one above the other on a base 28 at the lower end of the tube. The cathode base 28 may be connected externally to a terminal of a direct voltage source which is preferably at zero or ground potential. The cathode emissive material is coated on the upper cathode element 20, one form of which includes a plurality of concentric ring-shaped vanes 30 to aid in providing uniform emission and discharge current. An adjacent -heater coil 32 provides the necessary heat for the cathode. The outermost portion extending above the cathode forms a focus bafile 34 which directs the discharge in the desired path toward the anode and provides further protection from the emissive material. A second inner centrally positioned cathode baflle plate 36 similarly shelds an adjacent planar auxiliary electrode 38 from the emissive coating and directs the discharge path 18 around the auxiliary electrode.

Electrode 38 is centrally positioned across the tube 3,327,166 Patented June 20, 1967 within the cathode section, but may be at a potential of about 2 kilovolts with respect thereto. An axially extending insulated lead 40 from the auxiliary electrode passes through the bafile and cathode and is connected by a terminal 42 through the base 28 to an external source of direct voltage. The electrode 38 is preferably further connected through an external current limiting resistor 44 to the same source 46 of trigger pulses as that of grid 16 or alternatively may be connected to a separate pulse source synchronized with the grid pulses. The pulse source 46 may be any suitable known device which provides pulses of direct voltage. The grid potential is also preferably the same as that of the auxiliary electrode while the anode potential may be in the order of 50 kilovolts. Application of the trigger pulse to both the grid and auxiliary cathode electrodes, or a pulse on the grid in conjunction with a substantially constant potential on the auxiliary cathode, causes ionization in both areas which results in a more rapid occurrence of a discharge to the anode at lower power levels. The added electrode acts to prime the discharge path with the main control of the tube firing potential continuing to be provided by the grid 16. In addition, the delay time is relatively independent of the power level at which the tube is operated. The novel arrangement has resulted in improvements in the order of 50% in the reduction of firing time and an even greater percentage reduction in the variation with changes in power.

It may thus be seen that the present invention provides a simple, efiicient control of the discharge tine of a gas thyratron. While only a single embodiment has been illustrated, the invention is not to be considered as limited to the exact form or use shown and many other variations may be made in the particular design and configuration without departing from the scope of the invention as set forth in the amended elairns.

What is claimed is:

1. A gas discharge device comprisng:

an envelope containing a gas therein;

an anode at one end of the envelope;

a control grid spaced from the anode;

a base having leads therethrough at the other end of said envelope for connection to potential means;

an emissive coated cathode adjacent said other end of the envelope, a portion of the cathode structure extending therefrom toward said grid and forming a discharge path between the cathode and anode;

means applying a first potential to the anode with respect to the cathode;

a planar auxiliary electrode positioned centrally across the envelope between the grid and cathode within said extended portion thereof and having a lead extending axially through said cathode and base; shielding means positioned centrally across said envelope between said cathode and auxiliary electrode for directing said discharge path around said auxiliary electrode and means applying second smaller potentials to said grid and auxiliary electrode with respect to said cathode, said means applying second potentials including;

means applying trigger signals to said grid to cause said ,gas to discharge at a predetermined potential level.

2. The device of claim 1 wherein said grid includes an opening and a center portion forming a circuitous discharge path from said cathode and shielding said anode from said emissive coating.

3. The device of claim 2 wherein said shielding means includes a bafile, said lead from said auxiliary electrode extending therethrough.

4. The device of claim 3 including a heater coil underlying said cathode.

5. The device of claim 4 wherein said grid and auxiliary electrode are connected to the same potential and trigger means, and a current limiting resistor is con-' nected in series With said auxiliary electrode.

6. A gas discharge device comprising:

an envelope containing a gas therein;

an anode at one end of the envelope;

a control grd spaced from the anode;

a base having leads therethrough at the other end of said envelo pe for connection to potential means;

an emissive coated cathode adjacent said other end of the envelope, a portion of the cathode structure extending therefrom toward said grid and forming a discharge path between the cathode and anode;

a planar auxiliary electrode positioned centrally across the envelope between the grid and cathode within said extended portion thereof and having a lead extendng axially through said cathode and base;

shielding means positioned centrally across said envelope between said cathode andauxiliary electrode for directing said discharge path around said auxiliary electrode; and means applying potentials to said anode, grid and auxiliary electrode with respect to said cathode to cause said gas to discharge at a predetermined potential level.

References Cited UNITED STATES PATENTS 2,514,l65 7/1950 Ramsay 313-193 2,831,999 4/1958 Doolittle 313-197 X 2,942,1 36 6/1960 Cook et al. 313-193 X 2,948,825 -8/1960 Riley et al. 313--197 X 3,l65,660 1/1965 Menown 313-197 X JAMES W. LAWRENCE, Primay Examiner.

P. C. DE'MEO, Assistant Exam'ner. 

6. A GAS DISCHARGE DEVICE COMPRISING: AN ENVELOPE CONTAINING A GAS THEREIN; AN ANODE AT ONE END OF THE ENVELOPE; A CONTROL GRID SPACED FROM THE ANODE; A BASE HAVING LEADS THERETHROUGH AT THE OTHER END OF SAID ENVELOPE FOR CONNECTION TO POTENTIAL MEANS; AN EMISSIVE COATED CATHODE ADJACENT SAID OTHER END OF THE ENVELOPE, A PORTION OF THE CATHODE STRUCTURE EXTENDING THEREFROM TOWARD SAID GRID AND FORMING A DISCHARGE PATH BETWEEN THE CATHODE AND ANODE; A PLANAR AUXILIARY ELECTRODE POSITIONED CENTRALLY ACROSS THE ENVELOPE BETWEEN THE GRID AND CATHODE WITHIN SAID EXTENDED PORTION THEREOF AND HAVING A LEAD EXTENDING AXIALLY THROUGH SAID CATHODE AND BASE; SHIELDING MEANS POSITIONED CENTRALLY ACROSS SAID ENVELOPE BETWEEN SAID CATHODE AND AUXILIARY ELECTRODE FOR DIRECTING SAID DISCHARGE PATH AROUND SAID AUXILIARY ELECTRODE; AND MEANS APPLYING POTENTIALS TO SAID ANODE, GRID AND AUXILIARY ELECTRODE WITH RESPECT TO SAID CATHODE TO CAUSE SAID GAS TO DISCHARGE AT A PREDETERMINED POTENTIAL LEVEL. 